Process for reactivating a spent silicamagnesia cracking catalyst



Jan. 27, 1959 .1.k s. MELIK ET AL PROCESS FOR REACTIVATING A SPENTSILICA-MAGNE CRAGKING cATALYsT Filed April 16, 1953 70 FLUE GAS F001 ERS4A/0 2,871,195 SIA F//vfs Pfam/FRY HfRMAA/ E R15/SIR.

PROCESS FOR REACTIVATING A SPENT SILICA- MAGNESIA lCRACKING `CATALYSTJohn S. Melik, Hammond, Ind., and Herman E. Ries, Jr., Chicago, Ill.,assignors to Sinclair Refining Company, New York, N. Y., a corporationof Maine Application April 16, 1953, serial No. 349,289

6 yCintas. (ci. 252-411) Our pending application Serial No. 79,674, ledMarch 4, 1949, now abandoned, discloses water treatment of small poresilica-magnesia cracking catalysts to improve surface area and activity,and it claims a method for improving the cracking capacity of thecatalysts by water treatment and the improved silica-magnesia crackingcatalysts and cracking processes resulting from application of ourmethod. Our present invention relates to water treatment ofsilica-magnesia cracking catalysts and is spcciiically concerned withmethods for improving their susceptibility to regeneration by burning oicarbonaceous matter deposited thereon during the cracking process andthe application of this improvement to the regeneration step ofpyrolytic conversion processes utilizing silicamagnesia catalysts toimprove their coke burning capacity. This application is acontinuation-in-part of our application Serial No. 102,816, filed July2, 1949, now abandoned.

Application Serial No. 79,674 points out that we have discovered that aconventional silica-magnesia cracking catalyst may be contacted withwater to effect remarkable increases in cracking activity and surfacearea while maintaining in some instances improved selectivity withrespect to product distribution. Both virgin catalyst and equilibriumcatalyst; i. e. catalyst that has reached an equilibrium activity valuethrough continued use, regeneration and re-use; respond to this Watertreatment. In that application we emphasized application of watertreatment to regenerated catalysts, i, e. catalysts in which the cokedeposited thereon during a cracking process has been burned olf, becausewe consider that the best way to apply water treatment commerciallyeither to maintain a high catalyst activity for the catalyst inventoryor to permit more severe regenerating conditions and thus greater cokeburning capacity in regeneration by compensating for activity and arealosses. We have now discovered, however, that water treatment of spentsilicamagnesia cracking catalysts directly improves their carbon burningrates, i. e. the rates at which carbon deposited on the catalysts can beburned off during regeneration. For example, water treatment for 24hours at 212 F. of DA-S silica-magnesia catalyst bearing about 2.4weight percent of carbon increases the burning rate almost threefold at1100 F. and somewhat less, say about two-fold, at 1050 F. regenerationtemperature. This improved carbon burning rate of silica-magnesiakcatalysts is eX- tremely important since one of the principal drawbacksin using these catalysts is their low burning rate during regenerationwhich requires excessive amounts of air andY reducing capacity.Accordingly, this application is directed to water treatment of spent orused silica-magnesia ment in coke burning capacity is the dominantconsideration. i

We have found that if the desired increase in carbon burning rate of thesilica-magnesia catalysts is to be obtained the presence of some liquidphase water in contact with the surface of the catalysts in the treatingoperation is essential. The catalysts may be contacted with water in acontinuous phase or they may be treated with steam under conditions oftemperature and pressure which will insure the contact of thecatalystwith water in the liquid phase. For instance, We have -foundvthat treatment with low pressure steam so that capillary condensation iselected produces effective results and represents a particularlyadvantageous method for applying Water treatment to commercial crackingcatalysts. Of course7 catalysts in a commercial unit is at hightemperatures, e. g. about 900 F. when leaving the reactor of a fluidcatalyst unit; therefore, it is necessary to pass the catalyst to anintermediate cooling zone if superatmospheric pressures in the treatingzone are to be avoided. Accordingly, we recommend the use of atmosphericpressure for convenience in handling but our improvement is obtainedunder the conditions of either reduced or elevated pressures as long asthey are sucient to insure the contact of liquid phase water with thecatalyst surface during its treatment.

The temperature of our catalyst treatment should be maintained betweenabout 150 to 600 F. We have found that a moderately high temperature,say within the approximate range of 150 to 200 F., is an especiallydesirable condition for effecting the catalyst treating operation. Athigher temperatures, say upwards of 500 to 600 F., catalyst area beginsto fall off slightly. When steam is used as a catalyst contact medium itis desirable to vary the temperature from 212 to 600 F. with thepressure being sufficient to insure the presence of liquid phase water.

The concentration of water to catalyst in our treatment may be variedVovera wide range without materially affecting the results obtained. Wehave used a ratio of about 4:1 by weight of water to catalyst in smalllscale work for convenience and ease of manipulation. The water tocatalyst contact time in the treating zone may vary from several minutesto about hours asl long as this contacting time is suicient to elect asubstantial increase in the carbon burning rate of the catalyst.Although 24 to 60 hours of water treatment yappear to produce maximumimprovement we have obtained substantial increases in carbon burningrate after a very short period of water to catalyst Contact. Preferably,we consider that a contact period of at least about onehalf hour shouldbe maintained for best results. The factor of contact time is, ofcourse, a variable alfording the operator control over the extent ofimprovement in carbon burning rate effected. lt is therefore importantin a sense that at least several minutes are required to produce thedesired result while longer periods depending upon the temperatureutilized are usually necessary to effect substantial increases in carbonburning rate.

In order to show that the improvement effected by the water treatment ofsilica-magnesia catalysts as claimed Y may not be eitected by treatmentwith steam, experiments have been performed which show that the treat-`ment claimed is substantially inoperative unless Water in the liquidphase is present. For instance, steam treatment under conditions oftemperature and pressure pre- 'the silica-magnesia type crackingcatalysts are uniquely susceptible to improvement by the Water treatmentof our invention. These experiments establish that our method isapplicable only to silica-magnesia catalysts as opposed to otherconventional catalysts such as silica-alumina and natural clay types.

'fables I to IV set forth the results of these experiments. It should benoted that each series or samples was treated under comp-arableconditions except as spe/siiioally noted. Catalyst area was measured bythe well known Brunauer-Emmet-Teller nitrogen adsorption method.Cracking activity was determined by the well known `Jersey D-l-L benchscale test method on a standard gas oil sample. Activities marked withan asterisk are estimated from area-activity correlation diagrams. Inthe tables the commercial catalysts used are further identifiable asfollows:

Catalyst Type Weight Analysis fluid-synthetic MgO, 75% SiOz.

silica-magnesia.

do MgO, 65% Si0-z.

fluid-acid treated 15% A1203, 72% S102, balnatural clay. ance MgO, CaO,FeiO;

and S04'. 11% A1203, 89% S102.

Aerocat fluid-synthetic silica alumina.

signicant increase in the catalyst area and specific cracking activity,but causes a two to threefold increase in the specic burning rate of thecatalyst. This result is sharply contrasted with the results oftreating` other catalysts than silica-magnesia catalysts according toour invention. For example, when a sample of equilibrium Filtrolcatalyst was subjected to water treatment under comparable conditions,the catalyst area increased from to 140 square meters per gram, theD-l-L activity increased from 26.5 to 29.0 and the carbon burning rateremained substantially unchanged, changing from 48 to 49 pounds carbonper hour per ton of catalyst.

rllhe area and pore structure of the catalyst appears to -be importantwith respect to improvement in burning rate. Thus t-he burning rate ofDA-S silica-magnesia catalyst, having an average pore radius of about 16angstrom units (1l langstroms for the virgin catalyst), improved morethan two-fold after water-treating for regeneration at 1050 F., whilethe burning rate of Filtrol natural clay catalyst containing 1.58%carbon of much larger pore size range (80% above 20 to 25 angstrom unitsin radius) improved only slightly `after water treatment lforregeneration at 1050 F. These results may be related to the majorincrease in cracking activity and surface area that accompanies watertreatment of silicamagnesia catalyst compared to the minor improvementin activity and area effected by water treatment of clay type catalyst.Nalco silica-magnesia catalyst, having pore radii of about 14 Kand 2langstrom. units for the virgin and equilibrium materials closelyapproximates DA-S silica-magnesia in response to water treatment.

The data of Table II illustrates that steam treatment of virgin crackingcatalysts under conditions not admitting capillary condensation or inany other manner permitting the presence of liquid phase water does nothave a The above table shows that water treatment of equilibriumsilica-magnesia cracking catalyst not only effects beneficial eiect oncatalyst area yand cracking activity but rather has a deleteriouseffect.

TABLE Il Steam treatment of virgin cracking catalysts Steam TreatmentCatalyst Area, D-i-L Activity sq. mJg- Catalyst Temp., Time, Press.,Before After Before After F. hrs. p. s. i. g.

A. 1, 24 1, OOO-300 578 302 56.0 26. 5 B. 1, 150 23 400 578 299 56. 030. 5 C. 1, 175 24 400 318 128 51. 0 22. 5 D. 1, 250 24 0 271 128 43. 323. 5 E. 1, 205 24 60 271 72 13. 3 17. 0 F. Aerocat 1, 050 24 75 651 141*56. 0 *24. O

evince The following table shows the elect of our ywater treatment onthe saine samples of virgin cracking catalysts..which were steamde-activated in Table II. 'The letters identifying each sample ofcatalyst in Table III represent the steam fle-'activated product of thecorrespondingly by lettered sample of virgin catalyst listed in TableII.

TABLE III Water treatment of steam deactivated virgin cracking catalystWater Treatment Catalyst Area, D-I-L Activity sq. :1L/g` 'l CatalystTime Before After Before After Hrs.

A. 24 302 464 26. 5 58. 5 B. 24 299V 508 C. 24 128 355 22. 5 50.0 D. 24l 128 136 23. 5 25.0 E. 72 72 17.0 *17.0 F. Aerocat 212 24 141 153 *24.0*26.0

This data illustrates that Water treatment of steam deactivated virginsilica-magnesia catalyst has the opposite effect of steam treatment andrestores both lost area and activity to the silicamagn'e'sia catalystbut has little beneficial eect on the natural clay and silica-aluminacatalysts tested. l

TABLE IV Steam treatment of `equilibrium silica-magnesiaI catalyst(Nalco) The tests of Table IV illustrate the effect on equilibriumcatalyst area by treatment according to our claimed process (A and B):compared with the elect by treatment with steam under conditions notproviding capillary condensation 'or the presence of liquid phase water.In order to illustrate this effect further, an additional experiment wasperformed under comparable conditions to the experiments in Table IV,employing a temperature of 600 to 610 F. at a pressure of 1700 p. s. i.to insure capillary condensation. `The treatment was carried out for aperiod of I62/2, hours at the end of which a nitrogen determination ofcatalyst area was made. ltwas found that unlike the similar test(Example D in Table IV in which no capillary condensation took place)equilibrium Nalco catalyst so treated increased in area from 295 squaremeters per gram to 491 square meters per gram which was an increase ofthe same order as observed in examples A and B which were carried outfor three to four times as long a period of time. v-

The following examples illustrate certain aspects of our invention butare not intended to be limiting with respect to the conditions or modeof application. In the examples, familiar commercial silica-magnesiacatalysts are treated, which may be prepared by various methods usuallyinvolving precipitation or deposition or co-precipitation of magnesia onor with silica gel. See Elkin, Shull and Roess, 1nd, Eng. Chem, 37, 327(1945),

for example.

EXAMPLE I A lS-gram sample of spent DA-S silica-magnesia cata- 5 lystfrom pilot plant processing containing about 2.4% 'carbon wasregenerated and required 0.901 cubic feet of air for 62 minutes atapproximately 580 C. (1076 F.) catalyst temperature to reduce thepercent carbonA to 0.16%. When a IS-gram sample of this catalyst wastreated with water for 24 hours at 212 F., the catalyst was regeneratedto 0.12% carbon on catalyst with only 0.375 cubic feet of air in 35minutes at a somewhat lower catalyst temperature.

EXAMPLE II A second sample of an equilibrium DA-S silica-magnesiacatalyst, which contained about 2.4% of highly refractory carbon, wastreated with Water for 24 hours at 212 F. When the carbon was burned off.in a small.

quartz reactor, in which' a lluidized bed was maintained by passage ofthe measured volumes of regenerating air, it was determined that theburning ratehad been increased about three-fold at a regeneratingtemperature of 1100D F. and about twofold at a regenerating temperatureof 1050 F. by the water treatment. The area, activity and burning rate(in pounds of carbon per hour per ton of catalyst per p. s. i. of O2partial pressure) data follow:

Gas Factor Relative Activity D-l-L Carbon Area,

Factor sq.m./g.

bon Removal 71 48 bib Formed C Orl C 0 ratio (At 1,100 F.) (At 1,050F.)

C-l33 A. Before Water Treating. 0. 3088 Il. 4

B. After Water Treating...

. builtup in successive reaction and regeneration cycles isl much `morerefractory in regeneration than carbon deposited in laboratorycarbonization. v

One method of applying our improved catalyst treatling process tocommercial cracking processes is il1ustrated in the laccompanyingdrawing representing schematically the flow of catalyst and oil in themajor elements of a fluid catalyst type unit. Preheated charge oil ischarged to reactor 16 by means of reactor riser 11. Freshly regeneratedcatalyst from regenerator 12 is continuously added to ythe, charge oilstream by means of regenerator standpipe 13. The mixture of charge oiland catalyst enters rector 10 through cone shaped distributing plate 14and forms a dispersed phase or bed in the reactor. Catalyst separatingfrom the dispersed phase falls to the bottom of the reactor and iswithdrawn through stripping well 15 in which it is contacted with steamas by line 16 to remove adherent oil. The reaction vapors pass overheadfrom reactor 10 through a nest of cyclone separators 17 by line 18 to afractionating system (not shown). Catalyst separated in cyclones 17 isreturned to the catalyst bed by means of dip leg 19. Stripped catalystordinarily is passed to regenerator 12 by line 20 and regeneratorriser-21 assisted by carrier air introduced as at 22. According to ourinvention a slip stream of spent catalyst isV continuously orintermittently withdrawn from line 20 by means of line 23 to treatingdrum 24. Since the'catalyst is at high temperature and it is necessarythat the treatment include some contact, if only through capillarycondensation, of catalyst with liquid phase water, a cooling water sprayis provided as at 25. Waste steam is introduced to treating drum 24 bymeans of line 26 and waste steam is released overhead through line 27.

Treated catalyst may be directly charged to the regenerator as byregenerator riser 21, but if the catalyst is superlicially wet it isusually desirable to dry the catalyst in order to maintain owability.Treated catalyst then may be passed from treating drum 24 by line 28 torotary drier 29 in which it is contacted countercurrently with hot air,superheated steam, ue gas or other hot inert gas. The heating gas isadmitted to drier 29 through line 30 and is released through line 31.Treated catalyst is withdrawn from drier 29 through line 32 toregenerator riser 21.

Where relatively small quantities of spent catalyst are water treated,the material may be handled as a slurry and be admitted directly toregenerator 12. However, where relatively large quantities of watervapor would be released within the regenerating system it is usuallydesirable to dry the catalyst after water treatment, or alternativelymaintain the treating conditions in drum 24 such that contact withliquid phase Water is effected predominantly by -capillary condensationthrough the use of steam at or just above the boiling point.

Although the drawing illustrates the application of 4our invention to afluid catalyst cracking system, it -is applicable to cracking processesemploying other schemes for catalyst handling. Por example, pelleted orbead catalyst used in moving bed or fixed bed processes may be treatedaccording to our invention. Indeed, pelleting silica-magnesia catalystsmay lower the burning rate in which event water treatment is especiallyadvantageous. With fixed bed processes, it is generally more convenientto treat the entire body of catalyst, but with moving bed processes aswith uid catalyst or suspension systems, we consider it desirable totreat only a portion of the catalyst inventory, as by continuouslydrawing oi a slip stream of spent catalyst leaving the reactor andpassing it through i a vessel equipped with means for cooling, treatingand drying the catalyst. For example, countercurrent contact with thecooling, treating and drying media may be elected in sections set olf bya system of conventional grids and distributing plates designed tomaintain uniform flow.

Hence, our present application represents a continuation-in-part of ourapplications Serial No. 79,674 and Serial No. 102,816 in applying watertreatment to spent silica-magnesia cracking catalysts where improvementin regenerator coke burning capacity is the primary concern. Since cokeburning capacity is probably the severest limiting factor on improvingconversion levels and in utilizing fully and most economically thesilica-magnesia catalysts of high cracking activity, the advantages ofprocesses devoted specically to improving the carbon burning rates ofthese cracking catalysts are evident.

We claim:

1. A method of treating spent silica-magnesia cracking catalysts whichcomprises treating the spent catalyst with water under conditions ofelevated temperature of from about 150 F. to about 600 F., a pressure atleast sufficient to insure the presence of liquid phase water in contactwith the catalyst surface during the treatment at said temperature, andcontact time ranging from several minutes to about 60 hours which issutlicient to eiect a substantial increase in the carbon burning rate ofthe catalyst.

2. A method of treating spent silica-magnesia cracking catalysts whichcomprises treating the spent catalyst with water under conditions ofelevated temperature of from about 212 F. to about 600 F., a pressure atleast suiicient to insure the presence of liquid phase water in contactwith the catalyst surface during the treatment at said temperature, andcontact time ranging from several minutes to about 60 hours which issucient to eiect a substantial increase in the carbon burning rate ofthe catalyst.

3. A method of treating spent silica-magnesia cracking catalysts whichcomprises treating the spent catalyst with saturated steam underconditions of temperature not exceeding 600 F., a pressure at leastsuflicient to insure the presence of liquid phase water in contact withthe catalyst surface during the treatment at said temperature, andcontact time ranging from several minutes to about 60 hours which issufficient to eiect a substantial increase in the carbon burning rate ofthe catalyst.

4. The method of regenerating a spent silica-magnesia cracking catalystcontaining carbonaceous material deposited on the catalyst by conversionof petroleum hydrocarbons in the presence of said catalyst, whichcomprises treating the spent catalyst with water under conditions ofelevated temperature of from about F. to about 600 F., a pressure atleast suicient to insure the presence of liquid phase water in contactwith the catalyst surface during the treatment at said temperature, andcontact time ranging from several minutes to about 60 hours which issufficient to etect a substantial increase in the carbon burning rate ofthe catalyst, and burning carbonaceous materials from said treatedcatalyst.

5. The method of regenerating a spent silica-magnesia cracking catalystcontaining carbonaceous material deposited on the catalyst by conversionof petroleum hydrocarbons in the presence of said catalyst, whichcomprises treating the spent catalyst with saturated steam underconditions of temperature not exceeding 600 F., a pressure at leastsucient to insure the presence of liquid phase water in contact with thecatalyst surface during the treatment at said temperature, and contacttime ranging from several minutes to about 60 hours which is sufficientto effect a substantial increase in the carbon burning rate of thecatalyst, and burning carbonaceous materials from said treated catalyst.

6. The method of claim 1 in which the temperature is about 150 to 200 F.

References Cited in the file of this patent UNITED STATES PATENTS

1. A METHOD OF TREATING SPENT SILICA-MAGNESIA CRACKING CATALYTS WHICHCOMPRISES TREATING THE SPENT CATALYST WITH WATER UNDER CONDITIONS OFELEVATED TEMPERATURE OF FROM ABOUT 150*F. TO ABOUT 600*F., A PRESSURE ATLEAST SUFFICIENT TO INSURE THE PRESENCE OF LIQUID PHASE WATER IN CONTACTWITH THE CATALYST SURFACE DURING THE TREATMENT AT SAID TEMPERATURE, ANDCONTACT TIME RANGING FROM SEVERAL MINUTES TO ABOUT 60 HOURS WHICH ISSUFFICIENT TO EFFECT A SUBSTANTIAL INCREASE IN THE CARBON BURNING RATEOF THE CATALYST.